Live presentations including audio and/or video and/or images are often generically called “multimedia” or simply “media.” A presently popular “media” application is to digitize audio and video clips. Typically, media is digitized using a video capture application. A video capture application converts analog video signals, such as those generated by a video camera, into a digital media format signal and then stores the digital signal on a computer's mass storage system. Typically, video capture from analog devices requires a special video capture card that converts the analog signals into digital signals and compresses the data. Such video capture cards usually capture video and audio. Thus, as used herein, “video” may include video information and its associated audio information.
Alternatively, external video capture devices exist that capture video signals from an attached camera and transfer them to a computer via a communications cable. The external video capture devices are often desirable because they are easier to install and use than internal devices. Therefore, they are usually preferred by a less-experienced computer user. Examples of such external video capture devices include “QuickClip” by Logitech; “In Video USB Capture” by Focus Enhancements; “InterView USB” by Interex, Inc.; and “USB Live! Video Adapter” by Nogatech Inc.
When an external device is used, the media (i.e., video and/or audio and/or images) signal is typically compressed within the external device before the signal is sent to the coupled computer. The signal is compressed because the communications connection between the device and the computer typically has a limited bandwidth. The computer-device interface normally cannot transmit the uncompressed media signal at the rate that the device receives the signal. Compressing the media signal allows it to flow smoothly and without loss across the limited-bandwidth connection to the computer.
If the computer-device interface was capable of transmitting the uncompressed media signal, the signal may overwhelm many existing computers. They are simply not powerful enough to process such a large amount of data in such a short time period. Most of the conventional, external, video-capture devices use a proprietary media-compressing scheme. They proprietarily compress the media data and transmit it to the computer. The computer simply stores the proprietarily compressed media data into a file. Alternatively, using proprietary software on the computer, the media data is decompressed. After the media data is decompressed, it is recompressed and stored using a standard media file format, such as MPEG, QuickTime, or Windows Media Format (which is also called ASF for advanced streaming format, active stream format or advanced system format).
The media data is recompressed to save space on the computer's mass storage system. The media data is stored in a standard media file format so that it may usable by a large array of general-purpose media applications.
Considering an ASF file as exemplary, it contains one or more multimedia streams, as disclosed in U.S. Pat. No. 6,041,345. A multimedia stream contains the data for one particular part of the overall ASF file. For instance, a typical ASF file might contain three multimedia streams, one containing the audio data for the file, another containing the video data for the file and a third containing markers and/or executable script to allow to synchronization with the audio and video playback. Playback of an ASF file (either over a network or via the local hard drive) is done by playing the data from one or more of the multimedia streams. In the past, these files have been manually assembled separately capturing the multimedia streams and manually or automatically (via software) combining and synchronizing various multimedia streams.
One problem posed by manual assembly of separate streams is capturing a live presentation in such a way that it can be transmitted as immediate streaming media, such as an ASF file.
For these reasons, there is a need for a system and method for facilitating the simultaneous capture of a live multimedia presentation including audio, video and synchronization events to allow for the playback of the captured audio and video and the synchronized changes to the image presentation as part of the live multimedia presentation.